A typical thermos has a thin vacuum space between the shiny inner flask and the

Question

A typical thermos has a thin vacuum space between the shiny inner flask and the shiny protective outer flask. The vacuum space is excellent at preventing: (a) Conduction (Explain) (b) Convection (Explain) (c) Radiation (Explain) (d) Conduction and convection (Explain) (e) Conduction, convection and radiation (Explain) A typical thermos has a thin vacuum space between the shiny inner flask and the shiny protective outer flask. The vacuum space is excellent at preventing: (a) Conduction (Explain) (b) Convection (Explain) (c) Radiation (Explain) (d) Conduction and convection (Explain) (e) Conduction, convection and radiation (Explain) (a) Conduction (Explain) (b) Convection (Explain) (c) Radiation (Explain) (d) Conduction and convection (Explain) (e) Conduction, convection and radiation (Explain)

Explanation / Answer

Adding Vacuum between the layers implies absence of any material there and since Conduction requires direct transfer of energy through physical contact of surfaces, conduction can be prevented in a typical thermos.

Convection is heat transfer due to bulk movement of molecules within a gas or a liquid. Since vacuum is added between the layers, these molecules will not be able to leave their given region as they require a medium to propagate (which is absent here due to the vacuum). Thus convection is stopped.

Radiation will escape since electromagnetic waves do not require a medium for its propagation. Therefore, the answer is [d].

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